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It has been demonstrated by scanning tunneling experiments and tight-binding calculations that zigzag-shaped graphene boundaries support peculiar edge states in the absence of any external magnetic field. We propose an effective "relativistic" model where such edge states arise as a consequence of pseudospin triplet p-wave pairing induced by a topologically nontrivial boundary condition at the graphene edge. Our approach establishes a direct (and rather general) connection between broken discrete symmetries of the problem and the observed behaviour of the tunneling density of states. We also point out that a phenomenon similar to the Little-Parks effect can potentially be realized in zigzag-terminated graphene. |
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